Separated Chrome results into flagged and unflagged values

Now, Chrome features only available with the user-side "Experimental Javascript Features" flag are marked with a special "flagged" cell, and do not contribute to its ES6 support percentage. This basically closes #188 and #257.

The "flagged" cell's colour is red with a green corner triangle, to vaguely suggest that the red field is "peeling off" revealing green underneath.